Disadvantages mentioned above are eliminated significantly by the removable card for a contactless communication consisting of a chip, basically a flat external body of the card made of electrically nonconductive material and card contacts which basis, according to this invention lies in the fact that the antenna comprises at least one thread of a conductive path on external nonconductive surface of the card's body and is at least partially overlaid by ferromagnetic material layer.
The location of the antenna and the creation of a conductive thread on the external surface of the body of the card improve the antenna attributes. Antenna's overlay by a ferromagnetic material layer solves the problem with card shading and stabilizes the antenna tuning.
After inserting into a slot of a particular device a substantial part of the card is electromagnetically shaded by metal pieces of the slot. Un-shaded remains mainly the cross-section of the entrance gap of which area is too small concerning the small thickness of the memory cards. Application of a ferromagnetic material on the card represents a significant element with suitable physical attributes in relation to signal transmission and of which areal spread creates conditions to control and forward the electromagnetic field from the surrounding towards the antenna on the card's surface. To gain desired receiving and transmission attributes it is suitable if the ferromagnetic material layer on the opposite side to the side of contacts reaches up to a marginal zone of the card's body area, preferably up to the edge of the card. From the technological point of view it is easy and suitable if the ferromagnetic material covers the whole area of the card apart from the contacts.
To maintain the standardized proportions of the removable cards within the stated tolerance should the sum of the superelevation height of the antenna's conductive path above the area surface of the card's external body and the thickness of the ferromagnetic material layer be no bigger than 0.15 mm, favorably up to 100 μm. Then it is possible to use the removable card according to this invention in slots of common removable memory cards with no necessity to develop and produce an external body of the card with special proportions. Ferromagnetic material relative permeability to the vacuum is from 30 to 180, favorably in a range from 50 to 150.
In advantageous adjustment the antenna is created on one surface of the card (upper or lower) by six to ten, favorably eight threads of the conductive path and both surfaces of the card are covered by a layer of a ferromagnetic material. In fact the antenna is placed between the two ferromagnetic material layers.
From the point of view of good transmission attributes it is appropriate if the conductive path threads have the width from 75 to 125 μm, favorably 100 μm. In one possible adjustment has the ferromagnetic material layer a form of a foil with the width from 75 to 125 μm, favorably 100 μm. Advantageous is if the ferromagnetic material layer consists of a ferritic foil for instance with the compound of ferric oxide Fe2O3, possibly Fe3O4 with the divalent metals.
As for solution with one antenna it is suitable if the threads are placed spirally on the area of a quadrilateral shape. From the technological point of view the corners of such structure will be curved. One side of the quadrilateral reaches up to the marginal zone of the card's body area on the opposite side to the side of contacts, preferably up to the edge of the card. It means that the antenna's edge is placed on that edge of the card's body which is, after inserting into an appropriate slot basically outside the slot, actually as close as possible to the external edge of the slot so in fact on the edge through which the card is taken out. The opposite side of the quadrilateral does not exceed two thirds, favorably the half of the card's body area height and the lateral sides of the quadrilateral reach up to marginal zones of the card's body area, preferably up to the edge of the card. Such adjustment allows a good use of such part of the card's area which contributes to a stabile electromagnetic wave transmission. Use of deeper located part of the card to hold the antenna's area can be unproductive or even worsening the total transmission attributes.
From the point of view of using a widespread microSD format of the cards advantageous is the adjustment when the described area of the antenna is of an orthogon shape, preferably a rectangle with the parameters of 3.5 mm to 6.5 mm times 6 mm to 10 mm, favorably 5 mm times 8.5 mm.
From the tuning point of view it is advantageous if the antenna is connected to the series with an element with capacity for instance a capacitor. This serial resonant circuit is tuned in for the frequency of 13.0 to 15.0 MHz after inserting the body of the card into an appropriate slot, favorably the frequency 14 MHz. Antenna is connected to the series with the resistance placed on the opposite side to the location of the element with capacity. The resistance is from 10Ω to 18Ω, favorably 14Ω. In contrast to the up to now used methods of processing the antenna signal is in the solution, according to this invention suitable if the signal is read between the first and the second thread from the side to which an element with capacity is connected to. The complex input impedance of the receiving circuit is Xf=14 MHz=4000Ω−j2200Ω at the frequency of 14 MHz.
The external body of the card is made of subsidized thermoplastic, preferably of a polymer type of PA6/6T and/or LCP and/or PBT and/or PET which creates a good condition to groove dredging with the sufficient adhesion of the conductive path to the groove surface. To reach an equal effect the body of the card can be at least covered with a layer of above mentioned materials on the places where the conductive path runs. The value of the used layer should reach at least the value of the conductive path height.
The removable card can have the adjustment containing two antennas shaped as a spiral induction coil located opposite on the card's body area outside the zone of contacts and the coins are joined through metallic gaps in the body of the card. On the card the connection is made on the place with no obstructions by inner elements of the card with original arrangement. Both areas of the card are covered by a ferromagnetic material reaching up to the edges of the card—to the end of the areas which are opposite to the zone of contacts. Ferromagnetic foils are found at the border of the entrance gap of the slot and are not electromagnetically shaded by the metal parts of the slot case. Such adjustment creates a funnel-shaped effect of electromagnetic field flow.
Other adjustment of the antenna's element is the solution when the conductive path of the antenna is across the circumference winded up on the card's body. The thread of the conductive path crosses the area of the card's body aslant and/or with the curvature continuous along the edge of the body of the card to the opposite area of the card's body from where crosswise to the other edge of the body of the card. According to the amount of the threads, this way it is repeatedly wind up onto the body of the card. The course of the conductive path on the surface of the card's body is vertical to the edge of the body of the card and needed movement of the neighboring threads is created on the edge of the card's body in a slope or curvature shape of the conductive path. Such adjustment creates an induction coil with the threads in both projections—vertical and parallel to the area of the card. Due to this construction it is possible to receive and transmit electromagnetic field in both mentioned directions. In case of problems with a contactless transmission of a signal via herein described removable card it is improvable if the mobile communication device is approached with the location of the removable card to the appropriate communication component for instance to POS terminal and the antenna is capable to process the electromagnetic field radiated directionally near the transmitter. To reach a good efficiency of the threads it is suitable if the across the circumference winded up conductive paths are mutually parallel.
When using two antennas the first contact of the first antenna is connected to a chip, the second contact of the first antenna is connected to grounding as well as to the first contact of the second antenna and the second contact of the second antenna is connected to a chip. The whole system has two near resonant frequencies due to which it is tuned in for a wider range. The range is needed considering the untuned system after inserting the card into a slot of the device. The demanded final frequency is 13.56 MHz. Such frequency can be received by antennas without external influence of the surrounding are tuned in a different frequency in a range from 13.4 MHz to 13.7 MHz, favorably from 13.5 MHz to 13.6 MHz.
To increase the functional attributes it is advantageous if the removable card is a memory card, favorably in microSD or SD or mini SD format.
The subject of protection according to this invention is by itself the utilization of the above described removable card in the mobile phone for creating a contactless link for payment applications with the use of a mobile phone.
Disadvantages of the present status are significantly eliminated also by a method of production of the antenna on the body of the removable card from the electrically nonconductive material according to this invention, of which the bottom line is that first a groove in the shape of a conductive path is dredged on the surface of the card's body, favorably by means of a laser beam. The thickness of the dredge cannot damage the integrity of the body of the card, usually does not exceed the depth from 0.005 mm up to 0.05 mm. Consequently, the groove is filled with a conductive material, favorable with an alloy containing gold since the contacts of the antenna are connected to a chip and on the surface or on the surface of the both areas is applied a ferromagnetic foil at least partially covering the antenna. It is suitable if the groove is filled in with a conductive material up to the height of the surrounding surface of the card.
To reach a good adhesive link of the conductive path with the body of the card and for easier groove dredging it is advantageous if the groove is dredged up to the layer of subsidized thermoplastic layer, favorably of PA6/6T and/or LCP and/or PBT and/or PET. It can be achieved by the choice of the basic material of the body of the card or by applying a layer of desired material on the surface of the body of the card before dredging the groove.